Renewable energy sources are essentially inexhaustible, unlike fossil fuels that are finite. It is also widely held that the greenhouse gases released when fossil fuels are burned are contributing towards changes in our climate and rises in global temperatures therefore; by increasing the amount of renewable energy produced we are not only acting sustainably but also helping to protect the environment.
Hydro power is a commercial technology that already accounts for a significant proportion of the world's existing renewable output with most of this output produced by large scale hydro projects using turbines to exploit the potential energy of the fluid trapped behind a dam. The problem with this type of development is the ever increasing constraints placed upon land use, environmental concerns and the high capital costs.
Hydrokinetic energy is a largely under exploited yet significant global marketing opportunity for any new technology that can reliably deliver competitively priced electricity for the consumer. Recent historical precedents also indicate that any new technology must also satisfy the growing expectations of environmental interests, vested lobby groups and the local population before it has a realistic probability of being sanctioned by the local authorities as well as meeting environmental standards as set out in various EU directives and domestic legislation. This business sector is attracting a growing level of interest from companies globally, but no front runner has been identified and all of the existing systems have some form of commercial or design limitation.
Technological development of hydrokinetic devices can be traced back to the Roman Architect Vitruvius who deployed an undershot waterwheel. The Romans also constructed an impressive flour mill at Barbegal that deployed 16 overshot water wheels. Evidence also exists that suggests the Romans were the first to deploy a floating undershot waterwheel used to drive a flour mill on the Tiber River.
Most of the waterwheels no longer operate commercially, due to their low power output, but re-evaluation of this technology is of interest to many in the renewable energy sector who are attempting to merge new and old technologies. An example of this is the Darrieus, Savonius, Barrel and Flipwing rotors marketed by ‘Hydro volt’ in the USA.
There also exist commercial examples of axial flow turbines, vertical axis turbines and hybrid technologies, such as Archimedes screw type rotors. Prior art wheels and turbines are subject to great environmental and commercial scrutiny and often fail to deliver on these grounds.
The difficulty of developing a commercially viable and environmentally sensitive hydrokinetic device should not be underestimated, particularly as the sea is a very hostile environment. Storm damage due to high winds is well understood and sea water is very corrosive to most metals. Fouling by sea weed and other micro marine creatures is also a challenge that occurs in a matter of months. One particular challenge is maintaining electrical integrity, as long term subsea power cable integrity over rocks remains unresolved for devices needing a solid base for their foundation.
A further problem associated with prior art devices is ease of maintenance. Intervention costs are very high for subsea devices requiring a Diving Support Vessel (DSV) to recover the device. Floating devices typically do not need a (DSV) but frequently need to be recovered to a dry dock to make major repairs, such as damaged rotor bearings.
There remains a need in the art for an efficient, environmentally sound hydrokinetic device with good reliability and resilience.
It is an object of the invention to provide a hydrokinetic device which overcomes at least one problem associated with the prior art.